During the processing of silver halide color photographic materials, spent processing solutions are generally recovered and discarded as an overflow. However, the recovery and discarding of spent processing solutions can cause substantial environmental pollution and prevents conservation of natural resources used to produce these solutions. Also, recovery costs are significant. If these spent processing solutions (overflows) could be reused as a replenisher, these environmental and economical problems could be solved. In addition, since active components remaining in the overflow could be re-utilized, the amounts of chemicals needed for preparing a replenisher would be reduced as compared to preparing a fresh replenisher, thereby further reducing the cost of processing. Hence, extensive processing solutions in order make them reusable by correcting the changes caused by processing, generally by removal of accumulated components which adversely affect photographic properties and replacing the consumed components.
With respect to a bleach-fix bath used for processing of color photographic materials, various efforts have been made in order to develop techniques for regenerating spent bleach-fix bath.
A bleach-fix bath generally contains chemicals for at least three functions, e.g., an aminopolycarboxylic acid iron (III) complex serving as a bleaching agent, a thiosulfate serving as a fixing agent, and a sulfite serving as a preservative. The overflow of the bleach-fix bath additionally contains a silver ion produced by desilvering action and color developer components which have been carried over from the prebath. At the same time, the overflow further contains an iron (II) aminopolycarboxylate resulting from oxidation of silver to silver ion.
As described above, regeneration of a processing solution generally requires removal of harmful accumulated components and addition of consumed components. However, long standing problems remain effectively removing the accumulated components. In order to solve this problem, various regeneration systems for removing or reducing a silver ion resulting from desilvering have been proposed.
A regeneration method in which a spent bleach-fix bath is contacted with metallic iron (steel wool) is disclosed in Radiography, Vol. 29, pp. 256-259 (1963) and JP-A-48-3624 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"). According to this method, while silver ion contacted with a metallic ion is recovered as metallic silver to reduce the silver ion concentration, metallic iron is dissolved into a bleach-fix bath (as a strongly reducing iron (II) ion) thereby weakening the oxidizing ability of the bath. As regeneration is repeated, the dissolved metallic iron causes a large variation in the iron ion concentration, making it difficult to stably control the overall ion concentration. The more one tries to reduce the silver ion concentration, the more likely one is to encounter this problem.
A method for reducing a silver ion by electrolysis is described in JP-B-53-40491 (the term "JP-B" as used herein means an "examined published Japanese patent application"), JP-A-51-19535, JP-A-51-36136, and U.S. Pat. No. 4,014,764. In this case, too, either an iron (III) complex is reduced to an iron (II) complex or a sulfite ion is oxidized to a sulfate ion at the anode, which seriously fatigues the processing solution and, at the same time, reduces stability of the solution. This problem becomes more conspicuous as the amount of electricity is increased to raise the rate of silver recovery and to reduce the silver ion concentration in the bleach-fix bath.
A technique for removing a silver complex by adsorption onto an ion exchange resin is proposed in J. Appl. Photogr. Eng., Vol. 6, pp. 14-18 (1980). However, this method involves complicated operations for releasing an adsorbed silver complex from the resin to regenerate the resin. Additionally, it has the problems of producing large quantities of waste liquid and having a high operating cost.
Thus, conventional techniques for removing or reducing unnecessary components from a spent processing solution to make the solution reusable generally suffer from the problems of a lack of control of the final ratio of components the inability to analyze the components, the need for complex regeneration steps, and the requirement for large-sized equipment for regeneration.
JP-B-56-33697 and JP-A-50-145231 disclose a technique for regenerating an overflow, in which silver is not positively removed, but, when necessary, an equilibrium amount of accumulated silver ion is relatively reduced, for example, by dilution. This method is simple, easy, and cheap to carry out as requiring no special equipment for silver recovery.
However, this method, when used alone, has been bound to delay the desilvering step due to the accumulation of silver bromide precipitating out in large quantities and the additional accumulation of sulfate which, eventually, tends to cause an undesired staining, due to accumulation of developer components or poor color reproduction, thus suffering from the problem of unstable operating performance. When this method is utilized, particularly for reuse of a bleach-fix bath, there is accumulation of (1) a halide ion and silver ion, (2) an iron (II) aminopolycarboxylate and, (3) developer components or sulfate, resulting from oxidation of sulfite ion. It appears that some or all of these accumulated components act on each other, resulting in one or more of delayed desilvering, formation of a leuco cyan dye (which leads to poor color reproduction), deterioration of image preservability, and/or a particular thermal discoloration of a cyan dye. Such problems become more pronounced as a result of rapid processing.
Therefore, development of a technique for regenerating an overflow generally encounters difficulty and, in particular, regeneration of a bleach-fix bath remains problematic, due to the deterimental action of the components contained or accumulated.
In another context, JP-A-63-46460 discloses an image formation method in which a light-sensitive material having a specific degree of swelling (i.e., quotient obtained by dividing a wet thickness of photographic layers after immersion in distilled water at about 33.degree. C. for about 2 minutes by a thickness after drying) is used. According to this method, it is asserted that image preservability is not impaired (specifically, stain increase and light discoloration of a magenta dye are inhibited) even if the time for washing with water is reduced. However, this technique aims to solve the problems arising from insufficient washing of bleaching components and fixing components when the washing time is reduced. However, there is no suggestion of possible solutions to the above-described problems arising due to the accumulation of various components in a bleach-fix bath through repeated regeneration and reuse of a bleach-fix bath, such as insufficient desilvering, poor color reproduction, and thermal discoloration by a cyan image.